This disclosure relates generally to the field of power conversion for isolated systems. More particularly, this disclosure relates to an improved power conversion topology providing a transformerless alternating current (AC) line isolator.
In isolated systems, like flyback converters, the input circuitry (i.e., the “Primary Circuit”) and the output circuitry (i.e., the “Secondary Circuit”) are electrically isolated, i.e., not electrically/galvanically connected to each other. Flyback converters are commonly used as isolated battery chargers and/or front-end AC-DC and DC-DC converters in switch mode power supply applications. For example, a common flyback converter is a buck-boost converter including an inductor (transformer). A primary winding of the transformer is coupled to the input circuitry, and a secondary winding of the transformer is coupled to the output circuitry, thus providing the desired isolation between the input circuitry and the output circuitry.
Transformers provide the basic safety isolation (e.g., up to about 3,000 volts) in standard power converters, but have some design trade-offs. For example, transformers of the sizes used in these applications have only roughly 90% efficiency and are very challenging in terms of their construction and manufacturing. Further, transformers occupy a relatively large amount of volume and add a large z-height (i.e., depth) requirement to the design of AC-DC adapters.
In the embodiments described herein, systems and methods are proposed by which a transformerless AC line isolator is provided, which both significantly reduces losses in power conversion and allows for the miniaturization of the power converter design, due, at least in part, to the lack of the presence of a transformer.